Abstract. A central goal of our research program is the development of new catalytic platforms that provide access to highly enabling technologies for the construction of complex, medicinally relevant molecular scaffolds. In this regard, research efforts in my laboratory have recently been focused on exploring the application of photoredox catalysis to the field of organic chemistry. A key feature of photoredox catalysis is the ability to convert visible light into chemical energy through excitation of light-harvesting catalysts. The photoexcited catalysts can act as both a strong oxidant and reductant simultaneously, creating a unique reaction environment that my group has exploited in the development of previously elusive synthetic transformations. In particular, our group and others have shown that this distinct feature provide opportunities for the design of multicatalytic platforms combining photoredox with alterative catalytic manifolds. The merger of photoredox and transition metal catalysis has recently been established as a powerful platform, providing entry to mechanistic pathways that are inaccessible under `standard' transition metal catalysis conditions which are singly oxidative, reductive or neutral. Indeed, my group has demonstrated that this reaction paradigm can facilitate novel Ni-catalyzed technologies through modulation of the oxidation state of the transition metal catalyst and photoredox-mediated generation of versatile C- centered radical coupling partners. In this research proposal, we outline new directions for metallaphotoredox catalysis that exploit the distinct reactivity of different transition metal catalysts and use photoredox activation modes to facilitate the functionalization of `non-traditional' abundant cross-coupling partners. In Aim I, we propose the direct, selective functionalization of aldehydic C?H bonds through the merger of hydrogen atom transfer, photoredox and nickel catalysis. The objective of Aim II is develop a decarboxylative Ni-catalyzed hydrofunctionalization of alkynes to enable rapid access to complex olefins from simple starting materials. While Aims I-II focus on the merger of photoredox and nickel catalysis, Aim III envisions the development of a dual photoredox copper catalysis strategy for C(sp3)- trifluoromethylation. Here, we anticipate that photoredox catalysis will enable the use of both carboxylic acids and alcohols as radical precursors in this multicatalytic platform, resulting in methods for decarboxylative and deoxy- trifluoromethylation, respectively. In Aim IV, we propose to harness the ability of silyl radicals for halogen abstraction to develop a general protocol for the trifluoromethylation of aryl bromides. Aim V envisions the use of visible light-promoted cobalt catalysis to accomplish our goal of developing a protocol for the amidation of sterically encumbered aryl boronic acids via aryl radical generation. Finally, Aim VI proposes the development of general platform for decarboxylative C(sp3)?N and C(sp3)?O bond formation through the combination of copper and photoredox catalysis.